Expensive? Maybe, maybe not, if you had a grasp on the materials requirements for a sign to last for 20 to 40 years in a roadside environment; and some understanding of the legal liability issues, and some understanding of a "trade union only contractor personnel" construction environment drives costs up, perhaps you would be surprised at how reasonable the costs are.
Given how fickle people (and laws) are these days, designing a sign for a
20-40 year lifespan seems like it's probably a waste of money compared to giving signs, e.g., 5-10 year lives and replacing the few that aren't replaced due to changing laws anyway.My grandfather worked for an electric utility company years ago, and in the post-WW II years they installed power lines using some incredible criteria such as "design for a 10 year working life assuming power usage will double every 2 years" -- they kept that up for at least a decade or so until power usage increases stabilized to the *much* smaller values seen today.
Maybe, maybe not. Lets consider the maintenance costs of re-lamping traffic signals. There is a large push on now to switch from incandescent to LED modules, it comes with an energy savings of at least 6 to 1 for each signal head (however mounted) (a 6 kW intersection signal becomes a 1 kW or less signal). The real savings comes from changing the re-lamping schedule from
6 months to 6 to 10 years (especially in a labor cost dominated situation like this).Reconsidering the design rules they installed sufficient overcapacity that the future maintenance costs were reduced for nearly 40 years. The US has overrun that overcapacity, and now are paying the piper now for forgetting the lessons of the past.
Reasonable relative to, say, a gazebo, but not relative to a piece of cardboard tacked to a post. ;-)
Cheers! Rich
Here in San Francisco, at least 60% of the green traffic lights are visibly failing, with blocks of LED out and sometimes blinking feebly. They're all going to have to be replaced. Reds and yellows look fine.
John
Do you mean degrading instead of failing? Here in Sacramento i see some reds with groups of leds failed, and far fewer greens with failed groups. The indication is degraded, not totally failed (like an incandescent lamp would do). I estimate that Sac. started later.
Considering the expected lifetimes of the comparison objects? I rather think it reinforces my post.
Funnily-shaped blocks of led's either totally out or, less often, flashing pathetically, sometimes as much as 50% of the surface area out. I'm guessing there are ballpark a dozen independently-powered clusters in each light, for redundancy, probably series strings, and some of the led's have failed open. Since the red and yellows probably have similar electronics, it's likely the green led's themselves that are bad.
The 10 year relamping thing may be optimistic.
I'll try to take some pix... the patterns are interesting. Reds would be a lot easier to photograph, from inside a car.
Apparently many white led's fail (degradation here) in just a few thousand hours. The IR led's in optocouplers degrade with use, too.
John
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